The invention relates to a device for feeding molten plastic extrudates which emerge from dies to a discharge channel having a cooling water inlet which follows the dies, in which device the dies are arranged in at least two rows, in such a manner that in the discharge direction extrudates from one row and the other row are guided alternately, next to and at a distance from one another.
A device of this type is known from DE 26 55 840 A1. In this device, the extrudates from two rows of dies which lie parallel and next to one another are guided via an arrangement of discharge channels in which the extrudates from in each case one row of dies are fed to an associated discharge channel and the two discharge channels are arranged back to back with respect to one another. In order to provide the extrudates with the necessary guidance, the discharge channels each form an outwardly directed, rounded projection onto which the extrudates are pulled. At their lower end, the discharge channels are brought together, so that the extrudates come together next to one another in such a manner that in an intermeshing position, i.e. arranged alternately next to one another with regard to their associated row, they are passed onward to a pelletizer with a relatively short distance between them.
The invention is based on the object of making it possible to apply the principle of bringing together extrudates which ultimately lie relatively closely adjacent to one another in a device in which the plastic extrudates are guided via a single, sloping discharge channel.
This object is achieved, in conjunction with the preamble of patent claim 1, in that two collection channels, which are arranged one above the other, are interposed between the dies and the discharge channel, in such a manner that the extrudates emerging from one row of dies are in each case fed to the discharge channel as a group via one of the collection channels, the individual extrudates of the two groups meeting one another in an intermeshing position alternately and next to one another on the discharge channel and being guided onward by the latter.
On each of the two collection channels, the extrudates as a group are immediately superficially cooled by the corresponding cooling water inlet, so that after they leave the collection channels the extrudates can no longer stick to one another. The device according to the invention takes advantage of this in that, on account of the arrangement of the dies, initially on each collection channel the extrudates are guided as a group at a distance which prevents them from sticking to one another. However, since the dies of one row of dies are arranged offset with respect to the dies belonging to the other row of dies, the extrudates which are supplied from each collection channel and are relatively well spaced apart from one another come together on the discharge channel, with the distance between them which was previously maintained on the respective collection channel being reduced by half; however, on account of the cooling of their surfaces which has taken place in the meantime, this does not cause any problems and the extrudates are reliably prevented from sticking to one another on the discharge channel. However, the discharge channel can now carry twice the number of extrudates closely adjacent to one another compared to each collection channel, i.e. given the same width of discharge channel compared to the known device it is now possible for the discharge channel to guide twice the number of extrudates next to one another, with the result that the throughput of the device according to the invention with only one discharge channel is doubled compared to the known discharge channel arrangement, without the discharge channel having to be widened. This of course has an equally beneficial effect on the pelletizer, which is likewise able to process twice the number of extrudates without its width having to be increased.
To prevent further processing of extruded material which has been supplied from the dies and has not yet reached the required quality for further processing, the device is expediently configured in such a way that each collection channel is arranged so that it can be displaced between an operating position, in which the extrudates are collected by a collection channel and a start-up position, in which the extrudates are guided adjacently past the collection channel in question. Only when extruded material which is of a suitable quality for processing is supplied is this material, following displacement of the collection channels into the operating position, collected and supplied to the discharge channel for further processing.
The separation between extruded material which can be processed and extruded material which cannot be processed is facilitated by the fact that at least one collection channel is assigned a separating element which, when displaced through the drop line of the extrudates into the operating position, takes hold of the extrudates and then severs them. This type of separation of extruded material is referred to in EP 0 086 400 B1. A particular configuration of the device with a separating element which covers the dies advantageously consists in the fact that a separating element which covers the dies is provided above the uppermost collection channel, which separating element, during displacement from the operating position into the start-up position, severs the extrudates and, by means of a diverter element, guides the extrudates which continue to emerge away from the collection channels. The diverter element ensures that the extrudates made from material of insufficient quality are reliably diverted away from the device.
Exemplary embodiments of the invention are illustrated in the figures, in which: